The present invention relates to a method for making a new type of cathode, for gaseous discharge lamps, such as neon or argon gas filled lamps.
As is known, several problems are involved in making gaseous discharge lamps, mainly because of a quick increase of the lamp temperature which in turn causes a great thermal expansion of the metal cathode and the glass envelope which is susceptible to the easily broken.
In order to at least alleviate the above mentioned problem, the cathode must be precisely fitted in the tube glass envelope so as to be perfectly centered and insulated.
At present this problem is frequently solved by a method which comprises the steps of: (a) engaging a mica spacer collar, of circular crown shape, on the end edge of the metal cathode, (b) locking this mica collar against the end of the cathode by using a longitudinally perforated steatite plug member and (c) wrapping a mica sheet about the cathode so as to insulate the cathode from the envelope glass.
This known method, however, is very complex and expensive.